During engine non-fueling conditions in which at least one intake valve and one exhaust valve are operating, such as deceleration fuel shut off (DFSO), ambient air may flow through engine cylinders and into the exhaust system. In some examples, an exhaust gas sensor may be utilized to determine ambient humidity during the engine non-fueling conditions. It may take a long time for the exhaust flow to be devoid of hydrocarbons during the engine non-fueling conditions, however, and, as such, an accurate indication of ambient humidity may be delayed.
The inventors herein have recognized the above issue and have devised an approach to at least partially address it. Thus, a method for an engine system which includes an exhaust gas sensor is disclosed. In one example, the method includes, during engine non-fueling conditions, where at least one intake valve and one exhaust valve are operating: modulating a reference voltage of the sensor; generating an ambient humidity based on a corresponding change in pumping current of the sensor; and, during selected operating conditions, adjusting an engine operating parameter based on the ambient humidity.
By modulating the reference voltage and determining the change in pumping current while the air fuel ratio is still changing during non-fueling conditions, such as DFSO, the effect of the changing air fuel ratio may be nullified. As such, the ambient humidity may be determined in a shorter amount of time, as the exhaust air fuel ratio does not have to be stable before an accurate indication of ambient humidity may be determined.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.